Ventilstamme

Ventilstamme, or valve stem, is a component in a valve that transmits motion from an actuator or handle to the closure element. It typically passes through the valve bonnet and is sealed with packing or glands to prevent leaks. Depending on design, the stem may transmit linear motion to move a gate, disc, or plug, as in globe, gate, and needle valves, or it may transmit rotational motion to turn a ball in ball valves.

Construction and materials vary, but stems are usually metal—stainless steel, brass, bronze, or nickel alloys—and can be solid or hollow. They may be threaded at the top for a handwheel or actuator, and they pass through packing glands that accommodate movement while containing the fluid pressure.

Design variations include straight stems, rising stems (which move upward as the valve opens) and non-rising stems. Some stems connect directly to the closure member; others use an intermediate linkage. Material choice depends on the fluid, pressure, and temperature, as well as corrosion resistance requirements.

Maintenance involves inspecting and replacing packing, adjusting bonnet screws, and replacing worn stems or packing as needed. Common failure modes include stem wear or galling, packing leakage at the bonnet, corrosion, and misalignment that can damage seats or guides.

Ventilstamme is the general term in Germanic languages for the valve stem and is used in plumbing, process industries, and machinery. In internal combustion engines, valve stems connect to the cam or rocker mechanism and guide movement within valve guides, with seals to limit oil or gas leakage.